Infusion system and method which utilizes dual wavelength optical air-in-line detection

ABSTRACT

Infusion fluid is flowed through a fluid delivery line of an infusion system. Optical signals having different wavelengths are transmitted through the fluid delivery line. The transmitted optical signals having the different wavelengths are received. At least one processor determines whether air or infusion fluid is disposed in the fluid delivery line based on the received optical signals having the different wavelengths.

FIELD OF THE DISCLOSURE

This disclosure relates to an infusion system and method, whichtransmits and receives optical signals having different wavelengths todetect whether air is disposed in the infusion system.

BACKGROUND

Different types of infusion systems exist for detecting whether air ispresent in the infusion fluid. Some infusion systems currently use oneor more ultrasound sensors to determine whether air is present in thefluid disposed by the infusion system. However, some of these sensorsare sensitive to debris such as dirt or residue from the cleaningsolution being disposed in the sensor location on the fluid deliveryline, which may lead to inaccurate results. Similarly, some of thesesensors are sensitive to mechanical alignment or positioning, whichaffects their accuracy and long term stability.

A system and method is needed to overcome one or more issues of one ormore of the current infusion systems and methods in order to detectwhether air is in the fluid disposed by the infusion system.

SUMMARY

In one embodiment, an infusion system is disclosed for being operativelyconnected to a fluid delivery line connected to a container containingan infusion fluid. The infusion system includes at least two opticaltransmitters, at least one optical receiver, at least one processor, anda memory. The at least two optical transmitters are configured totransmit optical signals having different wavelengths through the fluiddelivery line. The at least one optical receiver is configured toreceive the optical signals having the different wavelengths transmittedfrom the at least two optical transmitters. The at least one processoris in electronic communication with the at least two opticaltransmitters and the at least one optical receiver. The memory is inelectronic communication with the at least one processor. The memorycontains programming code for execution by the at least one processor.The programming code is configured to determine whether air or theinfusion fluid is disposed in the fluid delivery line based on thereceived optical signals having the different wavelengths which arereceived by the at least one optical receiver.

In another embodiment, a method for infusing an infusion fluid isdisclosed. In one step, the infusion fluid is flowed through a fluiddelivery line of an infusion system. In another step, optical signalshaving different wavelengths are transmitted through the fluid deliveryline. In still another step, the transmitted optical signals having thedifferent wavelengths are received. In yet another step, at least oneprocessor determines whether air or infusion fluid is disposed in thefluid delivery line based on the received optical signals having thedifferent wavelengths.

In an additional embodiment, an infusion system is disclosed for beingoperatively connected to a fluid delivery line connected to a containercontaining an infusion fluid. The infusion system includes one opticaltransmitter, at least one optical beam splitter, at least two opticalbeam filters, at least two optical receivers, at least one processor,and a memory. The one optical transmitter is configured to transmit abroad spectrum optical signal. The at least one optical beam splitter isconfigured to split the broad spectrum optical signal into two separatebeams. The at least two optical filters are configured to filter the twoseparate beams. The at least two optical receivers are configured toreceive the filtered two separate beams. The at least one processor isin electronic communication with the one optical transmitter and the atleast two optical receivers. The memory is in electronic communicationwith the at least one processor. The memory contains programming codefor execution by the at least one processor. The programming code isconfigured to determine whether air or the infusion fluid is disposed inthe fluid delivery line based on the received filtered two separatebeams which are received by the at least two optical receivers.

The scope of the present disclosure is defined solely by the appendedclaims and is not affected by the statements within this summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the disclosure.

FIG. 1 illustrates a block diagram of an infusion system under oneembodiment of the disclosure.

FIG. 2 illustrates a side-cross-section view of one embodiment of twooptical transmitters transmitting, using alternative modulation of thetransmitters, separate, sequential, alternating optical signals havingdifferent wavelengths to an optical beam splitter which directs eachseparate, sequential, alternating optical signal along the same opticalaxis through a fluid delivery line, to a mirror which reflects eachseparate, sequential, alternating optical signal back through the fluiddelivery line to an optical receiver located on the same side of thefluid delivery line as the two optical transmitters and the optical beamsplitter.

FIG. 3 illustrates a side-cross-section view of another embodiment oftwo optical transmitters transmitting, using alternative modulation ofthe transmitters, separate, sequential, alternating optical signalshaving different wavelengths to an optical beam splitter which directseach separate, sequential, alternating optical signal along the sameoptical axis through a fluid delivery line to an optical receiverlocated on the opposite side of the fluid delivery line as the twooptical transmitters and the optical beam splitter.

FIG. 4 illustrates a side-cross-section view of another embodiment ofone optical transmitter transmitting a broad spectrum optical signal,using continuous transmission, through a fluid delivery line to a beamsplitter which splits the broad spectrum optical signal into two beamsthat each respectively pass through separate optical filters beforebeing received by separate optical receivers, with the opticaltransmitter being disposed on an opposite side of the fluid deliveryline as the beam splitter, separate optical filters, and the separateoptical receivers.

FIG. 5 illustrates a side-cross-section view of another embodiment oftwo optical transmitters transmitting optical signals having differentwavelengths which are pulsed in a sequential, alternating order througha first beam splitter or mirror, through a fluid delivery line, to asecond beam splitter or mirror which splits the optical signals intoseparate beams which are received by separate receivers, with the twooptical transmitters, and the first beam splitter or mirror beinglocated on an opposite side of the fluid delivery line as the secondbeam splitter or mirror and the separate receivers.

FIG. 6 illustrates graphs of one embodiment of a first opticaltransmitter being turned ON and OFF to transmit a first optical signalof one wavelength, and a second optical transmitter being turned ON andOFF at opposite times as the first optical transmitter to transmit asecond optical signal of a different wavelength.

FIG. 7 is a graph illustrating spectral scan results obtained for oneembodiment of a planar plastic material that was used in an infusionpump cassette.

FIG. 8 is a graph illustrating spectral scan results obtained foranother embodiment of the same plastic material that was used in theinfusion pump cassette of FIG. 7 with the exception that the plasticmaterial was concave.

FIG. 9 is a graph illustrating spectral scan results that were obtainedfor yet another embodiment of a silicone membrane, which is the mediacontaining the infusion fluid in the infusion system.

FIG. 10 is a graph illustrating spectral scan results that were obtainedfor another embodiment of a 0.9 percent sodium chloride solution thatwas delivered via a fluid delivery line of an infusion system.

FIG. 11 is a graph illustrating spectral scan results that were obtainedfor yet another embodiment of an Intralipid 20 percent (fat emulsion)solution that was delivered via a fluid delivery line of an infusionsystem.

FIG. 12 illustrates a flowchart for one method of signal acquisitionaccording to one embodiment of the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a block diagram of an infusion system 100 under oneembodiment of the disclosure. The infusion system 100 comprises: aninfusion container 102; a fluid delivery line 104; a pump device 106; aprocessing device 108; a memory 109; an alarm device 110 that generatesan audio, visual, or other sensory signal or the like to a user; aninput/output device 112; at least one optical transmitter 114; at leastone optical receiver 115; and a delivery device 116. The infusion system100 may comprise an infusion system such as the Plum™, GemStar™,Symbig™, or other type of infusion system.

The infusion container 102 comprises a container for delivering aninfusion fluid such as IV fluid or a drug to a patient 118. The fluiddelivery line 104 comprises one or more tubes (and optionally in someembodiments includes a cassette), connected between the infusioncontainer 102, the pump device 106, and the delivery device 116, fortransporting infusion fluid from the infusion container 102, through thepump device 106, through the delivery device 116 to the patient 118. Thefluid delivery line 104 may also be used to transport blood to thepatient 118 using the delivery device 116, as a result of a pumpingaction of the pump device 106. The pump device 106 comprises a pump forpumping infusion fluid from the infusion container 102 or for pumpingblood to the patient 118. The pump device 106 may comprise a plungerbased pump, a peristaltic pump, or another type of pump. In otherembodiments, the infusion system 100 may not contain a pump device andmay use the force of gravity to deliver the infusion fluid.

The at least one optical transmitter 114 is disposed adjacent to thefluid delivery line 104. The at least one optical transmitter 114 isconfigured to transmit optical signals having different wavelengthsthrough the fluid delivery line 104. In one embodiment, the transmittedoptical signals comprise near infrared spectrum light having varyingwavelengths ranging between 600 nanometers to 1,500 nanometers. Inanother embodiment, the transmitted optical signals comprise nearinfrared spectrum light having wavelengths ranging between 940nanometers to 1,050 nanometers. In still other embodiments, thetransmitted optical signals may comprise near infrared spectrum lighthaving varying wavelengths. In one embodiment, the at least onetransmitter 114 may transmit the optical signals having the differentwavelengths sequentially. The at least one optical receiver 115 isdisposed adjacent to the fluid deliver line 104 and is configured toreceive the optical signals having the different wavelengths transmittedfrom the at least one optical transmitter 114.

In one embodiment, the wavelengths of the optical signals transmitted bythe at least one transmitter 114 are chosen so that if air is disposedin the fluid delivery line 104 the air will have a substantially greaterimpact on one of the transmitted optical signals than on another of thetransmitted optical signals. For purposes of this disclosure, the term“substantially” is defined as being greater than 10%. In anotherembodiment, the wavelengths of the transmitted optical signals areoptimized for the particular type of the infusion fluid disposed in thefluid delivery line 104 to achieve maximum differentiation between theinfusion fluid being disposed in the fluid delivery line 104 and airbeing disposed in the fluid delivery line 104. In still anotherembodiment, the at least one optical transmitter 114 and the at leastone optical receiver 115 are modulated in order to achieve a high levelof immunity from the ambient light presence of background light sourcessuch as fluorescent light, light-emitting-diode light, etc. and toincrease signal to noise ratio of the signal acquisition system.

In one embodiment, the at least one optical transmitter 114 and the atleast one optical receiver 115 are disposed on opposite sides of thefluid delivery line 104. In another embodiment, the at least one opticaltransmitter 114 and the at least one optical receiver 115 are disposedon the same side of the fluid delivery line 104 and a reflective orrefractive surface 117 may be disposed on the opposite side of the fluiddelivery line 104 for reflecting or refracting the optical signalstransmitted from the at least one optical transmitter 114, through thefluid delivery line 104, back to the at least one optical receiver 114.In another embodiment, at least one optical beam splitter 119 may beused to split the optical signal(s) transmitted by the at least oneoptical transmitter 114.

The processing device 108, which comprises at least one processor, is inelectronic communication with the pump device 106, the memory 109, theat least one optical transmitter 114, the at least one optical receiver115, the input/output device 112, and the alarm device 110. The memory109 comprises programming code 111 for execution by the processingdevice 108. The programming code 111 is configured to determine whetherair or the infusion fluid is disposed in the fluid delivery line 104based on the received optical signals having the different wavelengthswhich are received by the at least one optical receiver 115. In oneembodiment, the processing device 108 includes the memory 109 and theprogramming code 111. In another embodiment, the processing device 108and the memory 109 may be separate components. The processing device 108also contains or is in communication with a clock.

In one embodiment, the programming code 111 is configured to determinewhether the air or the infusion fluid is disposed in the fluid deliveryline 104 based how a ratio of the received optical signals having thedifferent wavelengths which are received by the at least one opticalreceiver 115 compares to a threshold.

The alarm device 110 comprises an alarm, triggered or generated by theprocessing device 108, for notifying the clinician (also referred to as‘user’ herein) of when the infusion system 100 contains air. The alarmdevice 110 may be configured to stop the pump device 106 prior to asignificant amount of air being delivered through the fluid deliveryline 104 and the delivery device 116 to the patient 118.

The input/output device 112 comprises a device, which allows a clinicianto input or receive information. The input/output device 112 allows aclinician to input information such as: medication information regardingthe infusion fluid being delivered from the infusion container 102;infusion information regarding the infusion of the infusion fluid beingdelivered from the infusion container 102; the selection of settings forthe processing device 108 to apply in using the programming codecontaining the algorithm(s); or other information that is pertinent tothe infusion. The input/output device 112 may allow a clinician toselect and/or confirm a user-inputted medication infusion program to beapplied by the processing device 108. The input/output device 112 mayfurther output information to the clinician. In other embodiments, anyof the information inputted into the input/output device 112 may bepre-installed into the programming code or the processing device 108. Inanother embodiment, the information may be remotely programmed into theprocessing device 108 from a remote computer or the input/output device112 may be a remote and/or portable computer.

The delivery device 116 comprises a patient vascular access point devicefor delivering infusion fluid from the infusion container 102 to thepatient 118, or for delivering blood to the patient 118. The deliverydevice 116 may comprise a needle, a catheter, a cannula, or another typeof delivery device. In other embodiments, the infusion system 100 ofFIG. 1 may be altered to vary the components, to take away one or morecomponents, or to add one or more components.

FIG. 2 illustrates a side-cross-section view of one embodiment of twooptical transmitters 114 transmitting optical signals having differentwavelengths to an optical beam splitter 119 which directs the separateoptical signals along the same optical axis through a fluid deliveryline 104 to a mirror 121 which reflects the optical signals back throughthe fluid delivery line 104 to an optical receiver 115. In thisembodiment, the transmitted optical signals of differing wavelengths maybe pulsed in a sequential, alternating order. Throughout thisdisclosure, anytime the term mirror or optical beam splitter is used, inother embodiments any type of beam splitting device, reflective surface,or refractive surface may be substituted.

FIG. 3 illustrates a side-cross-section view of another embodiment oftwo optical transmitters 114 transmitting optical signals havingdifferent wavelengths to an optical beam splitter 119 which directs thetransmitted optical signals along the same optical axis through thefluid delivery line 104 to an optical receiver 115. The optical receiver115 is located on the opposite side of the fluid delivery line 104 asthe two optical transmitters 114 and the optical beam splitter 119. Inthis embodiment, the transmitted optical signals of differentwavelengths may be pulsed in a sequential, alternating order.

FIG. 4 illustrates a side-cross-section view of still another embodimentof one optical transmitter 114 transmitting continuously a broadspectrum optical signal having a spectrum of wavelengths through thefluid delivery line 104 to an optical beam splitter 119. The opticalbeam splitter 119 splits the optical signal into two optical beams (ortwo optical signals) which then each respectively pass through separateoptical filters 123 before being received by separate optical receivers115. The two optical filters 123 are configured to filter the twoseparate beams so that that the two separate beams have twodistinctively different wavelengths with respect to each other when theyreach the respective receivers 115. The optical transmitter 114 isdisposed on an opposite side of the fluid delivery line 104 as theoptical beam splitter 119, the optical filters 123, and the opticalreceivers 115.

FIG. 5 illustrates a side-cross-section view of still another embodimentof two optical transmitters 114 transmitting optical signals havingdifferent wavelengths through a first beam splitter or mirror 119,through the fluid delivery line 104 to a second beam splitter or mirror119 which splits the beam into two beams (i.e. two optical signals)which are received by separate optical receivers 115. The two opticaltransmitters 114 and the first beam splitter or mirror 119 are locatedon an opposite side of the fluid delivery line 104 as the second beamsplitter or mirror 119 and the separate optical receivers 115. In thisembodiment, the transmitted optical signals of different wavelengths maybe pulsed in a sequential, alternating order.

FIG. 6 illustrates graphs of one embodiment of a first opticaltransmitter 114 a being turned ON and OFF to transmit a first opticalsignal of one wavelength, and a second optical transmitter 114 b beingturned on and off at opposite times as the first optical transmitter 114a to transmit a second optical signal of a different wavelength.

With reference again to FIG. 3, the optical transmission T_(λ1) of thefirst optical signal having a first wavelength transmitted by theoptical transmitter 114, through the fluid delivery line 104 containingfluid, and to the optical receiver 115 is determined using the equationT_(λ1)=C (T_(tube), T_(fluid), T_(debris)). The equation illustratesthat the optical transmission T_(λ1) of the first optical signal is afunction of the optical transmission of the first optical signal throughthe fluid delivery line tubing T_(tube), through the fluid T_(fluid),and through the debris (i.e. dirt, residue due to cleaning solution,optical noise from ambient sources, etc.) build-up on the fluid deliverytubing T_(debris). Similarly, the optical transmission T_(λ2) of thesecond optical signal having a second different wavelength transmittedby the optical transmitter 114, through the fluid delivery line 104containing fluid, and to the optical receiver 115 is determined usingthe equation T_(λ2)=f (T_(tube), T_(fluid), T_(debris)). The equationagain illustrates that the optical transmission T_(λ2) of the secondoptical signal is a function of the optical transmission of the secondoptical signal through the fluid delivery line tubing T_(tube), throughthe fluid T_(fluid), and through the debris build-up on the fluiddelivery line tubing T_(debris).

The first optical signal S_(1λ1) detected by the optical receiver 115 isa function of the first original signal S_(oλ1) having the firstwavelength transmitted by the optical transmitter 114 and the opticaltransmission of the first original signal S_(oλ1) through the fluiddelivery line tubing T_(tube), through the fluid T_(fluid), and throughthe debris build-up on the fluid delivery line tubing T_(debris) asshown by the equation S_(1λ1)=S_(oλ1) f (T_(tube), T_(fluid),T_(debris)). The second optical signal S_(2λ2) detected by the opticalreceiver 115 is a function of the second original signal S_(oλ2) havingthe second different wavelength transmitted by the optical transmitter114 and the optical transmission of the second original signal S_(oλ2)through the fluid delivery line tubing T_(tube), through the fluidT_(fluid), and through the debris build-up on the tubing T_(debris) asshown by the equation S_(2λ2)=S_(oλ2) f (T_(tube), T_(fluid),T_(debris)). By taking a ratio of S_(λ1/λ2)=S_(1λ1)/S_(2λ2)=S_(oλ1) f(T_(tube), T_(fluid), T_(debris))/S_(oλ2) f (T_(tube), T_(fluid),T_(debris))=S_(oλ1) f (T_(fluid))/S_(oλ2) f (T_(fluid)) the portion ofthe signal effected by the fluid delivery line tubing and the debristransmissions cancel each other out since they remain the same duringthe optical signal reception process, and the resultant equation is afunction of the original signals and the fluid transmission.Furthermore, the fact that the two optical transmitters are operating onthe same optical axis and are modulated at a high frequency assuresmeasurement through the same section of the moving fluid. To illustratethis, the Nyquist theorem states the sampling rate of the photo detectormust be greater (at least twice) than the movement of the fluid in orderto ensure that each transmitted wavelength travels through the samesection of the fluid/air region. At a maximum flow rate of 1,000milliliters per hour, the fluid moves at a speed of 133.84 millimetersper second in a typical intravenous line tubing of 1.33 millimetersinside diameter for a PVC tubing. A 0.48 millimeter fluid column in a1.33 millimeter inside diameter tubing has a 1 microliter volume. Ifthis fluid column moves with a speed of 133.84 millimeters per second,the 1 microliter fluid column completely leaves the region in about0.003 seconds; thus, indicating a minimum sampling frequency of 666Hertz (e.g. 2*Nyquist frequency of 333 Hertz). Alternatively, a samplefrequency of minimum 666 Hertz is required to sample a 1 microliterfluid column in a 1.33 millimeter inside diameter IV tube. Lightemitting diodes (LEDs) can be modulated in the megahertz region and canadequately sample and accommodate virtually any flow rate utilized ininfusion therapies.

A simplified version of the equation when the fluid in the fluiddelivery line 104 is fluid comprises S_(λ1/λ2) _(_)_(fluid)=S_(1λ1)/S_(2λ2)=S_(oλ1) f (T_(fluid))/S_(oλ2) f(T_(fluid))=A_(fluid). A simplified version of the equation when air isdisposed in the fluid delivery line 104 comprises S_(λ1/λ2) _(_)_(air)=S_(1λ1)/S_(2λ2)=S_(oλ1) f (T_(air))/S_(oλ2) f (T_(air))=A_(air).The simplified equations illustrate that the ratios give differentdistinct values with A_(fluid) indicating that fluid is disposed in thefluid delivery line 104 and with A_(air) indicating that air is disposedin the fluid delivery line 104. As a result, these equations/ratios canbe used to detect when air is in the fluid delivery line 104. Theequations/ratios may give varying results for different fluids beingdisposed in the fluid delivery line 104 but are easily distinguishablefrom the results of the equations when air is disposed and present inthe fluid delivery line 104.

The Beer-Lambert Law (or Beer's Law) along with the proposed ratiometricmethod supports the instant disclosure. The Beer's Law relates theabsorption of light to the properties of the material through which thelight travels. Beer's Law states that there is an exponential dependencebetween the transmission of the light through a substance and theproduct of the absorption coefficient (i.e. in this case tubing,fluid/air, dirt, residue due to cleaning solutions, etc.) of thesubstance and the distance the light travels through the substance (i.e.optical axis). In particular, Beer's Law states that

${T = {\frac{I}{I_{0}} = e^{- {aL}}}},$where T is transmission, I is intensity, I₀ is initial intensity, α isabsorption coefficient, and L is the optical path length. The absorptioncoefficient is comprised of the absorption coefficients of the tubing,fluid/air/froth, and any residue due to the cleaning solutions or oiland dirt. More specifically, the equation can be rewritten for theintensities the optical receiver will “observe” from the two differentoptical wavelengths, namely /₁=/₀e^(−a) ¹ ^(L) and /₂=/₀e^(−a) ² ^(L),because L is a constant and as a result of the narrow separation of thedifferent wavelengths, a₁≡a₂. Taking the ratio of /₁ and /₂ cancels thecommon elements such as residue due to cleaning solution or oil anddirt, and the tubing material parameters leaving the equation to containonly the ratio of the initial intensities (which are known). Since thetransmitted wavelengths share the same optical path, tubing, residue(“noise”), and sample the same section of the fluid column, the onlysignificant difference is whether the sampled region contains air orair; thus offering immunity from noise and resulting in highsignal-to-noise. A similar approach holds true for all embodimentsdescribed in this disclosure including the use of at least onetransmitter and at least one receiver. The disclosure does not convey alimit on the number of transmitters or receivers which may be used inalternative embodiments.

Because this disclosure provides immunity from ambient noise (dirt,ambient light, residue from cleaning solutions, etc.) there exist theadvantage of self-calibration of the optical sensor. One method ofutilizing self-calibration in an infusion pump is to provide a baselinereading without the presence of the IV tubing (and cassette) and priorto loading the IV tubing (and cassette) into the infuser. Because thisdisclosure is not an amplitude-based optical sensor system, but rather aratiometric method, the initial baseline reading (without the presenceof the IV tubing and/or cassette) provides a reference reading. Thecurrent state of the art air sensors in the typical infusion pump isbased on ultrasound technology which does not provide the opportunity toself-calibrate the ultrasound sensor nor provide immunity to mechanicalchanges or external noise factors (dirt, etc.). Routine calibration istypically needed for these current state of the art air sensors ininfusion pumps as part of overall life-cycle management. The instantdisclosure does not require calibration in the field or at the servicefacility as the device automatically self-calibrates before every use.

FIG. 7 is a graph illustrating spectral scan results that were obtainedfor a planar plastic material that was used in an infusion pump cassettecomprising part of a fluid delivery line 104. Wavelength is plotted onthe X-axis and the percentage transmittance is plotted on the Y-axis.The graph shows that from about 400 nanometers to approximately 1,600nanometers the transmittance is above 70 percent with a slight dip ataround 1,600 nanometers, and returning to approximately 70 percentbefore indicating no transmittance as wavelength continues to increasewith the scan ending at approximately 4,000 nanometers. Thetransmittance is greater than 70 percent in the range of 1,000nanometers to 1,500 nanometers. FIG. 7 demonstrates that varying thewavelengths of the optical signals results in substantial changes intransmittance.

FIG. 8 is a graph illustrating spectral scan results that were obtainedfor the same plastic material that was used in the infusion pumpcassette of FIG. 7 with the exception that the plastic material wasconcave. Wavelength is plotted on the X-axis and the percentagetransmittance is plotted on the Y-axis. The graph shows that thetransmittance is greater than 80 percent in the range of 1,000nanometers to 1,500 nanometers. FIG. 8 demonstrates that varying thewavelengths of the optical signals results in substantial changes intransmittance.

FIG. 9 is a graph illustrating spectral scan results that were obtainedfor a silicone membrane material that was used in an infusion pumpcassette. Wavelength is plotted on the X-axis and the percentagetransmittance is plotted on the Y-axis. The graph shows that thetransmittance is greater than 40 percent in the range of 1,000nanometers to 1,500 nanometers. FIG. 9 demonstrates that varying thewavelengths of the optical signals results in substantial changes intransmittance.

FIG. 10 is a graph illustrating spectral scan results that were obtainedfor a 0.9 percent sodium chloride solution that was delivered via afluid delivery line of an infusion system. Wavelength is plotted on theX-axis and the percentage transmittance is plotted on the Y-axis. Thegraph shows that the transmittance is greater than 90 percent in therange of 400 nanometers to 1,800 nanometers. The optical axis length was1 mm. FIG. 10 demonstrates that varying the wavelengths of the opticalsignals results in substantial changes in transmittance.

FIG. 11 is a graph illustrating spectral scan results that were obtainedfor an Intralipid 20 percent (fat emulsion) solution used in a fluiddelivery line of an infusion system. Wavelength is plotted on the X-axisand the percentage transmittance is plotted on the Y-axis. The graphshows that the transmittance is minimal in the range of 400 nanometersto approximately 1,200 nanometers and then increases with wavelengthuntil the end of the scan at approximately 1,800 nanometers. The opticalaxis length was 1 nanometers. FIG. 11 demonstrates that varying thewavelengths of the optical signals results in substantial changes intransmittance.

FIG. 12 illustrates a flowchart of one embodiment of a method 120 forinfusing an infusion fluid. The method 120 may utilize the infusionsystem 100 of FIG. 1. In other embodiments, the method 120 may utilizevarying systems including but not limited to any system disclosedherein. In step 122, the infusion fluid is flowed through a fluiddelivery line of an infusion system. In step 124, optical signals aretransmitted having different wavelengths through the fluid deliveryline. In one embodiment, the different wavelengths of the opticalsignals were optimized for the particular type of infusion fluiddisposed in the fluid delivery line to achieve maximum differentiationbetween the infusion fluid being disposed in the fluid delivery line andair being disposed in the fluid delivery line.

In one embodiment, the optical signals comprise near infrared spectrumlight having varying wavelengths ranging between 600 nanometers and1,500 nanometers. In another embodiment, the transmitted optical signalscomprise near infrared spectrum light having varying wavelengths rangingbetween 940 nanometers and 1,050 nanometers. In other embodiments, thetransmitted optical signals may comprise light having varyingwavelengths. In another embodiment, the at least one optical transmittertransmitting the optical signals may be modulated in order to achieve ahigh level of immunity from the ambient light presence of backgroundlight sources such as fluorescent light, light-emitting-diode light,etc. and to increase signal to noise ratio of the signal acquisitionsystem. In step 126, the transmitted optical signals having thedifferent wavelengths are received.

In step 128, at least one processor determines whether air or infusionfluid is disposed in the fluid delivery line based on the receivedoptical signals having the different wavelengths. In one embodiment,step 128 comprises the at least one processor determining whether theair or the infusion fluid is disposed in the fluid delivery line basedon how a ratio of the received optical signals having the differentwavelengths compares to a threshold. In one embodiment, step 128comprises the at least one processor determining the transmittanceproperty of the infusion fluid or air in-between two spectral regions.In step 130, if the determination is made in step 128 that air is in theinfusion system an alarm is generated by the at least one processor 108and the alarm device 110 generates the appropriate sound or visualdisplay to notify the user. In one embodiment, step 130 may comprise theat least one processor turning off a pump of the infusion system if thealarm sounds.

In one embodiment, steps 124, 126, and 128 comprise: in step 124,transmitting a first optical signal having a first wavelength andtransmitting a second optical signal having a second wavelengthdifferent than the first wavelength through the fluid delivery line; instep 126, receiving the first optical signal and the second opticalsignal; and in step 128, determining with the at least one processorwhether air or infusion fluid is disposed in the fluid delivery linebased on the received optical signals having the different wavelengthswith the at least one processor finding that air disposed in the fluiddelivery line has a substantially greater impact on the received firstoptical signal than on the second received optical signal.

In one embodiment, steps 124 and 126 comprise: in step 124, two opticaltransmitters transmitting the optical signals having the differentwavelengths through the fluid delivery line; and in step 126, only oneoptical receiver receiving the transmitted optical signals having thedifferent wavelengths.

In one embodiment, steps 124 and 126 comprise: in step 124, two opticaltransmitters transmitting the optical signals having the differentwavelengths through the fluid delivery line; and in step 126, twooptical receivers receiving the transmitted optical signals having thedifferent wavelengths.

In one embodiment, steps 124 and 126 may utilize at least one opticaltransmitter and at least one optical receiver disposed on opposite sidesof the fluid delivery line. In another embodiment, steps 124 and 126 mayutilize at least one optical transmitter and at least one opticalreceiver disposed on the same side of the fluid delivery line, and areflective or refractive surface disposed on the opposite side of thefluid delivery line for reflecting or refracting the optical signalstransmitted from the at least one optical transmitter, through the fluiddelivery line, back to the at least one optical receiver.

In other embodiments, any number, configuration, orientation, orlocation of optical transmitters and optical receivers may be used. Instill other embodiments, an optical beam splitter may be used to directthe optical signals to travel along a common optical axis. In furtherembodiments, a reflective or refractive surface may be used to reflector refract the optical signals having the different wavelengths to theat least one optical receiver. In other embodiments, additionalcomponents may be used in combination with at least one opticaltransmitter and at least one optical receiver to assist in transmittingor receiving the optical signals. In other embodiments, the method 120may be altered to vary the order or substance of any of the steps, todelete one or more steps, or to add one or more steps.

Applicant has conducted testing using various infusion fluids (includingSodium Chloride 0.9 percent; Dextrose 50 percent; Intralipid 20 percent;and Egg White 4.7 percent) and various flow rates (including 250milliliters per hour; 500 milliliters per hour; and 1,000 millilitersper hour) to compare the results of using the optical system and methodof the disclosure to determine whether air is disposed in the fluiddelivery line of an infusion system versus using an ultrasound sensorsystem (piezoelectric crystal transmitter receiver pair interfaced withelectronic voltage sweep oscillator that sweeps through the sensor'speak coupling frequency) to make this determination. The testing hasrevealed that the optical system and method of the disclosure hassubstantial unexpected results over use of the ultrasound sensor. Use ofthe optical system and method of the disclosure resulted in animprovement in resolution, defined as the smallest bubble size thesensor can detect, for all of the tested infusion fluids at each of thevarious flow rates of up to 72 percent improvement over use of theultrasound sensor. Use of the optical system and method of thedisclosure resulted in an improvement in accuracy, defined as the rateof detection, for all of the tested infusion fluids at each of thevarious flow rates in a range of 6 to 72 percent improvement over use ofthe ultrasound sensor. Use of the optical system and method of thedisclosure resulted in an improvement in signal-to-noise calculation forall of the tested infusion fluids at each of the various flow rates in arange of 280 to 800 percent improvement over use of the ultrasoundsensor. Use of the optical system and method of the disclosure resultedin an improvement in dynamic range, defined as the difference betweenthe largest and smallest bubble the sensor was able to detect, for allof the tested infusion fluids at each of the various flow rates of up to10.7 percent improvement over use of the ultrasound sensor.

The Abstract is provided to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin various embodiments for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true scope of the subject matter described herein.Furthermore, it is to be understood that the disclosure is defined bythe appended claims. Accordingly, the disclosure is not to be restrictedexcept in light of the appended claims and their equivalents.

The invention claimed is:
 1. An infusion system including a fluiddelivery line that is operatively connected to an infusion containercontaining an infusion fluid, the infusion system comprising: the fluiddelivery line; a first optical transmitter configured to transmit afirst optical signal at a first wavelength through the fluid deliveryline; a second optical transmitter configured to transmit a secondoptical signal at a second wavelength that is different than the firstwavelength through the fluid delivery line; an optical receiverconfigured to receive the first optical signal and the second opticalsignal; a beam splitter configured to direct the transmitted firstoptical signal along a first optical axis and the transmitted secondoptical signal along a second optical axis through the fluid deliveryline, wherein the first optical axis and second optical axis overlapinside the fluid delivery line; at least one processor in electroniccommunication with the first optical transmitter, the second opticaltransmitter, and the optical receiver; and a memory in electroniccommunication with the at least one processor, wherein the memorycomprises programming code for execution by the at least one processor,and the programming code is configured to determine whether air or theinfusion fluid is disposed in the fluid delivery line based on thereceived first and second optical signals having the differentwavelengths which are received by the optical receiver.